XXIV.—Is there such a thing as Eozoon canadense? A microgeological investigation

THE ANNALS

AND

MAGAZINE OF NATURAL HISTORY.

[FOURTH SERIES.]

V

No. 100. APRIL 1876.

XXIV. — Is there such a thing as Eozoon canadense ?

A Microgeolog ical Investigation . By Otto Hahn*.

I.

At the time when the microscope began to find a more ex-
tended application in geology, came also the discovery of the
u Dawn animal” — Eozoon canadense ,as it has since been called.
How great was the delight excited when it was supposed that
at length the beginning of organic creation had been found !
The Darwinian theory wanted the corner-stone ; and there it
was. As by a miracle, the primaeval slime ( Urschleim ) had
presented itself in a mass of serpentine limestone, which ap-
peared just as the slime itself must have appeared; the film,
microscopic tubes of 0*002 millira. diameter were still there
wonderfully beautiful ; and, as Carpenter says : — u a precise
model of the most ancient animal of which we have any
knowledge, notwithstanding the extreme softucss and tenuity
of its substance, is presented to us with a completeness which
is scarcely even approached in any later fossil.”

Who could help being pleased at seeing with his own eye
tliis firstling of creation ?

In a time of general excitement and enthusiasm it is difficult
to preserve mental quietude. I have, however, attempted to

• Translated by W. S. Dallas, F.L.S., from a separate impression of
the Memoir in the f \Y u r tie mbergi sell o naturwissenschaftliche Jaln-es-
hefte,’ 1870 .

Ann. & Mag. N. Ilist . Scr. 4. Vol. xvii. 18

266 M. Otto Hahn on Eozoon canadense.

do this as I commenced a work which concerned not only natu-
ralists but men in general. Every one must feel that investi-
gations into the history of Creation are family affairs. Hence
the existence of some anxiety was not to be wondered at ;
but it excites more astonishment to see how easily many throw
off their clothing and spring into the stream. The nature and
method of my work may show that I did not commence with
preconceptions.

A very great deal has already been written on the question.
The results of my investigation have, I think, finally settled
it. By my investigation it is established that there is no
gigantic Foraminifer in serpentine limestone.

My investigations have shown that the most essential cha-
racters of the Foraminifera, the chambers and the test, are
not there, but that we have to do with pure rock-formations,
such as occur everywhere in serpentine. But if these two
characters are wanting, there remain only the canal-systems ;
and these I have also recognized in gneiss, and at the same
time discovered their real significance.

The zoologists may now furnish their reply. The material
that I have made use of I will with pleasure place in their
hands.

In order to let the opponents of the opinion maintained by
me give full expression to their views, I will allow Dr. William
Carpenter himself to speak. In his work L The Microscope
and its Revelations ’ (London, ed. 4, 1868) he describes and
discusses Eozoon as follows : —

II.

a §396. A most remarkable fossil, referable to the Forami-
niferal type, has been recently discovered in strata much older
than the very earliest that were previously known to contain
organic remains ; and the determination of its real character
may be regarded as one of the most interesting results of
microscopic research. This fossil, which has received the
name Eozoon canadense , is found in beds of serpentine lime-
stone that occur near the base of the Laurentian Formation*
of Canada, which has its parallel in Europe in the Funda-
mental Gneiss of Bohemia and Bavaria and in the very
earliest stratified rocks of Scandinavia and Scotland. These

* u This Laurentian Formation was first identified as a regular series
of stratified rocks, underlying the equivalents not merely of the Silurian,
but also of the Upper and Lower Cambrian systems of this country, by
Sir William Logan, the accomplished Director of the Geological Survey
of Canada.”

M. Otto Hahn on Eozoon canadense.

267

beds are found in many parts to contain masses of considerable
size, but tisually of indeterminate form, disposed after the
manner of an ancient coral-reef, and consisting of alternating
layers — frequently numbering more than fifty — of carbonate of
lime and serpentine (silicate of magnesia). The regularity of
this alternation, and the fact that it presents itself also between
other calcareous and siliceous minerals, haying led to a suspi-
cion that it had its origin in organic structure, thin sections of
well-preserved specimens were submitted to microscopic ex-
amination by Dr. Dawson of Montreal, who at once recognized
its Foraminiferal nature *; the calcareous layers presenting the
characteristic appearances of true shell, so disposed as to form
an irregularly chambered structure, and frequently traversed
by systems of ramifying canals corresponding to those of Cal-
carinci ; whilst the serpentinous or other siliceous layers were
regarded by him as having been formed by the infiltration of
silicates in solution into the cavities originally occupied by
the sarcode-body of the animal , — a process of whose occurrence
at various geological periods, and also at the present time,
abundant evidence has already been adduced. Although this
determination has been called in question, on the ground that
some resemblance to the supposed organic structure of Eozoon
is presented by bodies of purely mineral origin f, yet, as it has
not only been accepted by all those whose knowledge of Fora-
miniferal structure gives weight to their judgment, but has
been fully confirmed by subsequent discoveries \ , the author
feels justified in here describing Eozoon as he believes it to
have existed when it originally extended itself as an animal
growth over vast areas of the sea-bottom in the Laurentian
epoch §.

u § 397. Whilst essentially belonging to the Nummuline
group, in virtue of the fine tubulation of the shelly layers
forming the 1 proper wall ’ of its chambers, Eozoon is related
to various types of recent Foraminifera in its other characters.

• “ This recognition was due, as Dr. Dawson has explicitly stated in
his original memoir (‘Quarterly Journal of the Geological Society/ vol. xxi.
p. 54) to hi3 acquaintance not merely with the author’s [I)r. Carpenter’s]
previous researches on the Minute Structure of the Foraminifera , but
with the special characters presented b} r Calcarina , as exhibited in thin
sections which had been transmitted to him by the author.”

t “ See the Memoir of Profs. King and Kowney, in the Quart. Journ.
Geol. Soc. vol. xxii. p. 185.”

- J; “See Dr. Dawson’s account of a specimen of Eozoon discovered in a
homogeneous limestone, in Quart. Journ. Geol. Soc. vol. xxiii. p. 257.”

§ “ For a fuller account of the results of the Author’s own study of
Eozoon , and of the basis on which the above reconstruction is founded,
see his Papers in Quart. Journ. Geol. Soc. vol. xxi. p. 50, and vol. xxii.
p. 219, and in the ‘Intellectual Observer/ vol. vii. (18G5), p. 278.”

IS*

268 M. Otto Hahn on Eozoon canadense.

For in its indeterminate zoophytic mode of growth it agrees
with Polytrema ; in the incomplete separation of its chambers
it has its parallel in Carpenteria ; whilst in the high develop-
ment of its intermediate skeleton and of the canal-system by
which this is nourished, it finds its nearest representative in
Calcarina. Its calcareous layers were so superposed one upon
another, as to include between them a succession of 1 storeys 7
of chambers ; the chambers of each ( storey 7 usually opening
one into another like apartments en suite ; but being occasionally
divided by complete septa . These septa are traversed by

passages of communication between the chambers which they
separate, resembling those which, in existing types, are occu-
pied by stolons connecting together the segments of the sarcode-
body. Each layer of shell consists of two finely tubulated or
i Nummuline 7 lamella;, which form the boundaries of the
chambers beneath and above, serving (so to speak) as the ceiling
of the former, and as the floor of the latter ; and of an inter-
vening deposit of homogeneous shell-substance, which consti-
tutes the * intermediate skeleton. 7 The thickness of this
interposed layer varies considerably in different parts of the
same mass, being in general greatest near its base, and pro-
gressively diminishing towards its upper surface. The ‘inter-
mediate skeleton 7 is occasionally traversed by large passages,
which seem to establish a connection between the successive
layers of chambers; and it is penetrated by arborescent systems
of canals, which are often distributed both so extensively and
so minutely through its substance, as to leave very little of it
without a branch.

“ § 398. Now in the fossilized condition in which Eozoon is
most commonly found, not only the cavities of the chambers,
but the canal-systems to their smallest ramifications, are filled
up by the siliceous infiltration which has taken the place of
the original sarcode-body ; and thus, when a piece of this
fossil is subject to the action of dilute acid, by which its
calcareous portion is dissolved away, we obtain an internal
cast of its chambers and the canal-system, which, though
altogether dissimilar in arrangement , is essentially analogous
in character to the c internal casts 7 represented in figs. 258, 259.
This cast presents us, therefore, with a model in hard serpen-
tine of the soft sarcode-body which originally occupied the
chambers, and extended itself into the ramifying canals of
the calcareous shell ; and, like that of Polystomella , it affords
an even more satisfactory elucidation of the relations of these
parts, than we could have gained from the study of the
living organism. We see that each of the layers of serpen-
tine forming the lower part of such a specimen is made

M. Otto Ilalm on Eozoon eanadense.

269

up of a number of coherent segments, which have only
undergone a partial separation ; these appear to have ex-
tended themselves horizontally without any definite limit;
but have here and there developed new segments in a vertical
direction, so as to give origin to new layers. In the spaces
between these successive layers, which were originally occupied
by calcareous shell, we see the 1 internal casts ’ of the branch-
ing canal-system, which give us the exact models of the ex-
tensions of the sarcode-body that originally passed into them.
But this is not all. In specimens in which the Nummuline
layer constituting the 1 proper wall ’ of the chambers was
originally well picserved, and in which the decalcifying pro-
cess has been carefully managed (so as not by too rapid evo-
lution of carbonic-acid gas to disturb the arrangement of the
serpentinous residuum), that layer is represented by a thin
white film covering the exposed surfaces of the segments, the
superficial aspect of which as well as its sectional view are
shown in fig. 2. And when this layer is examined with a
sufficient magnifying-power, it is found to consist of extremely
minute needle-like fibres of serpentine, which sometimes stand
upright, parallel, and almost in contact with each other, like
the fibres of asbestos (so that the film which they form has
been termed the c asbestiform layer ’), but which are frequently
grouped in converging brush-like bundles, so as to be very
close to each other in certain spots at the surface of the film,
whilst widely separated in others. Now these fibres, which
are less than 1-1 0,000th of an inch in diameter, are the
‘ internal casts ’ of the tubnli of the Nummuline layer (a pre-
cise parallel to them being presented in the 1 internal cast *
of a recent Amphistegina in the author's possession); and their
arrangement presents all the varieties which have been de-
scribed ( § 391) as existing in the shells of Operculina. Thus
these delicate and beautiful siliceous fibres represent those
pseudopodial threads of sarcode, which originally traversed the
minutely tubular walls of the chambers ; and a precise model
of the most ancient animal of which we have any knowledge,
notwithstanding the extreme softness and tenuity of its sub-
stance, is thus presented to us with a completeness which is
scarcely even approached in any later fossil.

“ § 399. In the upper part of the ‘ decalcified * specimen
shown in fig. 2, it is to be observed that the segments arc con-
fusedly heaped together, instead of being regularly arranged
in layers, the lamellated mode of growth having given place
to the acervulinc . This change is by no means uncommon
among Foraminifera ; an irregular pi ling- together of the
chambers being frequently met with m the later growth of

270

M. Otto Hahn on Eozoon eanadense.

types whose earlier increase takes place upon some much more
definite plan. After what fashion the earliest development of
Eozoon took place we have at present no knowledge whatever ;
but in a young specimen which has been recently discovered, it
is obvious that each successive 1 storey ’ of chambers was
limited by the closing-in of the shelly layer at its edges, so as
to give to the entire fabric a definite form closely resembling
that of a straightened Peneroplis. Thus it is obvious that
the chief pecuBarity of Eozoon lay in its capacity of inde-
finite extension ; so that any single organism might attain
a size comparable to that of a massive coral. Now this, it will
be observed, is simply due to the fact that its increase by gem-
mation takes place continuously ; the new segments succes-
sively budded-off remaining in connection with the original
stock, instead of detaching themselves from it, as in Forami-
nifera generally. Thus the little Globigerina forms a shell
of which the number of chambers never seems to increase be-
yond ten , any additional segments detaching themselves so as
to form separate shells ; but by the repetition of this multi-
plication the sea-bottom of large areas of the Atlantic Ocean at
the present time has come to be covered with accumulations of
Globigerince , which, if fossilized, would form beds of limestone
not less massive than those which have had their origin in the
growth of Eozoon . The difference between the two modes of
increase may be compared to the difference between a plant
and a tree. For in the plant the individual organism never
attains any considerable size, its extension by gemmation being
limited ; though the aggregation of individuals produced by
the detachment of its buds (as in a potato-field) may give
rise to a mass of vegetation as great as that formed in the
largest tree by the continuous putting forth of new buds.”

III.

I commenced my investigations on three undoubtedly true
Canadian Serpentine limestones : —

I. A specimen for which I am indebted to the kindness of
Professor Hochstetter of Vienna. It came from Carpenter
himself, and still bears his ticket. It is 95 millims. long
and 50 millims. broad. It may be divided into three layers : —

1. Dolomite, 1-25 millims. ; 2, pure pale-green noble ser-
pentine (ophite), 25-35 millims. ; 3, broad bands of limestone
alternating with bands of serpentine 1 millim. broad, 35-55
millims. ; then follows a granular formation.

From all the parts of the stone thin slices were taken.
Carpenter regards layer 1 as the base.

M. Otto Hahn on Eozoon eanadense.

271

Under the microscope layer 1 presents a whitish transparent
amorphous matrix, and in this, traversing the stone in an
oblique direction so that but little of the matrix is to be seen,
hyaline crystals of dolomite, which, however, have their forms
not sharply developed. They have innumerable yellow en-
closures (picotite?). Sp. grav. 3T6, or that of dolomite.
The crystals lose themselves irregularly in

Layer 2, the pure serpentinous mass. Under the microscope
traversed by bands with parallel striation, which (in polarized
light) immediately prove to be chrysotile. Sp. grav. 2 5 5.
This layer is sharply discriminated from

Layer 3, the alternating layer. First a limestone band 5 mil-
lims. broad, then a serpentine band of equal breadth, and so
on. Limestone and serpentine bands, but constantly becoming
narrower, now alternate ; they are parallel, elongated, and cut
off perpendicularly at the lateral ends. The limestone bands
effervesce with dilute hydrochloric acid and dissolve rapidly
and completely . They therefore contain no silica. Sp. grav.
2*60. Distributed in the limestone, and more rarely in the ser-
pentinous mass, there are round and six-sided hyaline crystals.
These are arragonite. Here also are the canal- or branching-
systems. The latter, however, are not uniformly distributed
in the limestone, but only in particular granules (individuals).
I have found ten canal-systems to 7 cubic eentims. The mass
of these systems is white by direct, and light brown by trans-
mitted light. In many places the origin of the canal-systems
from the spot where the arragonite crystals are maybe distinctly
recognized. They are never continued into the chambers, and,
indeed, have no relation at all to these. Nay, they even thicken
towards them in their stolons. Their form I take to be well-
known.

What Carpenter calls the “ film,” is a chrysotile layer around
the serpentine. This layer I have observed in nearly all
ophites. The aciculjc are not tubes (even under the highest
magnifying-powers they contain no filling mass), but crystals .

Layer 4. Now follows granular structure. The serpentinous
mass is in part not even yet quite homogeneous. We distinctly
see granules with olivine-polarization and cracks , even traces
of a lamination . The passages cease both towards the sides
and upwards. The arragonites are still present ; but instead
of the canal-systems there are only fissures round about
the arragonite granules, filled with the same milk-white mass
of which the canal-systems in No. 3 consist.

TI. Hand-specimen in the collection of the University of
Tubingen. 50 mi Hi ms. long, 40 mi 11 inis, broad.

1-10 millims. serpentine alternating with threads of chry-

272 M. Otto Hahn on Eozoon cauadense.

sotile ; 10-25 millims. serpentine as in I. ; 25-28 millims. a
broad limestone band ; 29-40 millims. serpentine alternating
with limestone in nearly parallel bands, as in I. Seen from
the side, the bands lie in oblique lines ; the stone is therefore
probably composed of undulated layers.

The limestone varies from hyaline to milk-white ; both
colours are seen in bands side by side. The cleavages are
distinctly visible. The arragonite forms small points. The
remaining 10 millims. are of granular structure.

In polarized light the chrysotile at once catches the eye ; but
it is only necessary to make a rough section, and then the
white needles project from the matrix. Under the microscope
these chrysotile threads are seen almost every where on the
edges of the serpentine, but also in the limestone at its point
of contact with the serpentine, generally perpendicular to
both,

III. Hand-specimen in the collection of the University of
Tubingen, presented thereto by Professor von Hochstetter.
100 millims. long, 60 millims. broad. Has a round serpentine
spot at one end. This circle is surrounded by alternate layers
of serpentine and limestone. At the opposite side there is
likewise a similar round spot. Between the two there is a
paler band (also limestone), bent so that the white appears like
a note of interrogation. At the end dolomite. Sp. grav. pro-
bably as in I. 3.

In this specimen there are limestone fragments in the ser-
pentine passages. Several canal-systems may be seen even
with a power of 25 diameters ; in some it may be distinctly
perceived that they start from the disseminated arragonite.

What is particularly remarkable in this specimen is that
the limestone forms layers with canal-systems only in small
surfaces ; by far the greater part is granular with distinct fluidal
structure, which can only be the consequence of a strong pres-
sure. In consequence of this the layers also are broken up
into spherical masses and mixed up together. In many
places there are black points in the limestone ; these are
very probably graphite.

What follows applies to all the three specimens : —

The serpentine undoubtedly originated from olivine which
got into a mass of limestone while the latter was still soft.
When the decomposition took place quietly and no pressure
intervened, the serpentine would at first retain the form of
the olivine, but by further decomposition the soft granule
woiild first of all become squeezed flatter in consequence of
the pressure exerted by the overlying mass. If no way of
escape presented itself, or if an opposing pressure occurred

M. Otto Hahn on Eozoon canadense.

273

from the sides, cylinders with an elliptical section would be
formed, and by further pressure finally strata (layers) in the
limestone mass. But if, as in specimen III., unequal pres-
sure occurred, the layers must have been broken up and torn
to pieces ; but the parts would then, where they hardened, show
granular structure in their section. It cannot be asserted that
the intervening calcareous mass was hardened or even present
before the serpentine ; otherwise the fluidal structure would
no longer be explicable.

The canal-systems are of very different diameter ; they
also differ with regard to their distribution and form. They
consist of carbonate of lime. Nowhere do we see around
them an envelope like shell-substance, but they rather vanish
into the surrounding material.

I also investigated : —

IV. Serpentine limestone from the Bayerische Wald. The
sequence is limestone, limestone with graphite, limestone with
serpentine, granular as in III., serpentine, limestone with ser-
pentine, limestone with graphite. Distinct chrysotile layers
round the serpentine grains. No trace of canal-systems.

V. Serpentine limestone from Krummau (Bohemia), from
Professor von Hochstetter. 1. A similar specimen treated with
acid.

The limestone is coloured grey by black enclosures. A
large, much divided serpentine layer. The serpentine is
enveloped by a layer of chrysotile, which appears as a fine
white line. No canal-systems.

VI. Another serpentine limestone will be mentioned below.

All the serpentine limestones at command, especially from

Elba and Lissiz, were examined. Much as the latter re-
sembles II., no trace of the canal-systems could be found,
but there were chrysotile shells. With regard to the latter,
I refer the reader to Draschke, in Tschermak’s c Mineralo-
gische Mittheilungen,’ 1871, Heft i. p. 1.

Further, about thirty serpentines, from the pseudomorphic
crystals of the Snarum to the pure sedimentary rock, and,
lastly, all the primary limestones at my disposal were ex-
amined, and, finally, about twenty gneisses. In that of Mont
Blanc I recognized the canal-systems .

IV.

I regarded it as the simplest course, with respect to the
description of the Eozoon- rock, to allow its first investigator,
if not its discoverer, to speak. Little has been added to his
description of Eozoon canadense. G umbel thought he detected

274 M. Otto Hahn on Eozoon canadense.

wart-like superficial processes. Max Schultze states that after
the calcination of the rock the canal-systems were coloured
black ; and from this he concludes that their contents were of
organic nature.

I could only repeat what is well-known, if I were to repro-
duce here the present position of the controversy. Zirkel has
given a thorough representation of the contradictory opinions

Die mikroskopisehe Beseliaffenheit der Mineralien und
Gesteine,’ Leipzig, 1873, p. 313). As regards Max Schultze,
I may refer the reader to the i Verhandlungen des naturhisto-
rischen Yereins der Preussischen Rheinlande und Westphalens,’
Jahrg. xxx. p. 164, unfortunately an incomplete work of the
celebrated naturalist.

There are consequently two opinions. One maintains the
organic nature of Eozoon ; the other disputes it. The former
supports itself upon analogous facts in the animal kingdom,
both extinct and living. The latter holds that it can also cite
analogies in favour of the assumption of peculiar rock-forma-
tions. Few leave the question open.

I thought it best to adopt the following mode of investi-
gation.

I started from the proposition that for eveiy part of a rock
the presumption is in favour of mere rock- formation. If the
organic nature of a portion of the rock is affirmed, the onus
probandi lies upon those who make the assertion, and, until
full proof to the contrary, the presumption remains in force.

But in the present case we stand immediately in face of a great
difficulty. What are the characters of an organic being ? The
same structure, and especially the same structures together (as
is admitted by Carpenter and his allies), occur neither in extinct
nor in living organic creatures - but it is rather stated that the
individual parts of the Eozoon - structure are only to be recog-
nized in different kinds of Foraminifera.

This circumstance alone makes the proof very doubtful.
But to this must be added the further fact that the zoologists,
and especially the best of them, are least inclined, and indeed
least in a position, to know and test all existing rock-structures.
The position of the geologist is therefore all the more un-
favourable. His proofs are scarcely considered • and even other-
wise it is difficult to get their value as proof duly estimated ;
whilst the zoologist is in the happy position of being able to
throw into the scale the Brennus’s sword of authority, espe-
cially when the microscope is in question.

The position of the two can only be equalized if it be ad-
mitted that mere analogy is incapable of furnishing the proof
of the organic origin of Eozoon • and that, further, no part of the

M. Otto Halm on Eozoon canadense. 275

supposed organism can be recognized as mere rock-structure.
It is only if all the essential characters of the Foraminifer,
and indeed each for itself, are no mere rock-structures, that
the proof from analogy is carried at least to a high degree of
probability. But if the inorganic nature of only one is proved,
the chain of evidence is broken.

From all this the course of investigation becomes a matter
of necessity. All existing serpentine limestones (ophicalcites) ,
all serpentines and primary limestones by themselves, and,
further, also the minerals occurring under certain circumstances
in the serpentine limestone, must be investigated with respect
to their nature and their relations to the serpentine limestone.
But when this is done, a large field opens to the geologist.
Now the question is, do the J^ozocw-structures occur in any
other rock or not, whether with all the characters together or at
least some of them ? Upon this it becomes his duty to examine
microscopically as to this point all primary and metamorphic
rocks, nay, even the rocks of the whole sedimentary series. I
have followed the course indicated, and then, and not before,
allowed myself to form a judgment upon the zoological facts
which had been advanced. In what follows I shall undertake,
first, the criticism of the geological, then of the mineralogical,
and, lastly, of the zoological facts.

1. The Geological Facts .

The jFozocw-structures occur in lenticular or spheroidal
nodules of serpentine limestone in the limestone of the Lauren-
tian formation of Canada. The limestones belong to gneiss
strata, the earliest sedimentary rocks. They are mere enclo-
sures. Are they merely imbedded in the limestone, and there-
fore formed before it, or were they produced simultaneously
with it? This question can be decided only on the spot. Jt
is most probable that they were imbedded as ready-formed
nodules 5 but this is not necessary. If the serpentine-mass
was, as it must have been at the time of the formation of the
Eozoon , still in a fluid state, it must also have found other
cavities in the limestone, and have filled these. But we have
no account of any such cavities. Hence the first supposition
is the more probable.

Eozoon is said to occur not only in Canada, but also in the
most various parts of the earth. Gumbcl has found it in the
Bayerischc Wald, Ilochstcttcr in Bohemia (Krumniau), and
Pusgrewski in Finland. 1 have examined some of the hand-
specimens of the two first named and found in them no Eozoon -
structures, or at least not all the described characters together.

276

M. Otto Hahn on Eozoon canadense.

In these and a great number of serpentine limestones there
were everywhere the alternating layers of serpentine and lime-
stone, but nowhere the so-called canal- systems of the Canadian
Eozoon .

Upon this, however, I lay no great weight after the results
subsequently obtained. Where these canal-systems do not
occur, there is, as I must mention at once, no trace of proba-
bility for an organic structure.

According to a communication from King and Rowney,
ophicalcites occur even in the Lias of Scotland.

From the preceding statements it follows that even with
respect to the question whether ifosoow-structures exist, we
must carefully and in the first place ascertain quite clearly
what are the essential characters of Eozoon . If the investi-
gator lays especial stress upon the chambers or alternating
layers of serpentine and limestone, hewill find Ab^cm-structures
wherever serpentine occurs. I have such specimens out of
mineral deposits. I have a specimen of serpentine limestone in
which the two layers appear exactly in the same form as in the
Canadian specimens, but are 2 centims. instead of 1*5 millim.
in thickness.

I have, in the first place, to refer to the formation of ser-
pentine.

Serpentine is not an original, but a metamorphic rock. As
is well known, there is no rock which is so certainly the result of
metamorphism and can be derived from so many minerals as
serpentine ; Gustav Rose has shown that it may originate from
augite, hornblende, pyrope, and spinel. It probably originates
in the greatest masses from olivine, and, indeed, by the access
of water. Rut everywhere it occurs in association with lime-
stone ; and so the alternate layers of the two substances cannot
be in the least surprising.

I have investigated an immense number of serpentines, and
always found that they are products of metamorphism. Take
the Snarum pseudomorphs after olivine, in the interpretation
of which Prof. Quenstedt first proved his mastership. In these,
olivine grains, still undecomposed, lie in the olivine crystal,
which is now serpentine. The crystalline form has persisted ;
the olivine has been converted by access of water into ser-
pentine.

The basalts of the Swabian Alb (especially those of Eisen-
riittel) display in every hand-specimen the distinct picture of
the serpentinization of olivine. The Karfenblihl, near Det-
tingen, consists for the most part of such serpentine. In the
Canadian serpentine limestone also olivine grains are to be
detected with fragments of limestone in the serpentine. By

M. Otto Ilahn on Eozoon canadense.

277

this, of course, the filling of the chambers would immediately
be got rid of as an impossibility ; but it might be objected that
here the olivine grains are not quite certain, and the serpentine
bands, which are vermiform in their section, cannot be so easily
explained away.

But at the conclusion of my investigation I was so fortunate
as to obtain two specimens of serpentine limestone which re-
move all doubts. Their derivation is unknown to me ; but this
does not affect the matter ; at any rate, they are not from
Canada.

These specimens show in their interior exactly the same
serpentine layers’as the Canadian ones, and in section exactly
the same chambers ; but in the middle of the chambers are
the olivine grains , which still polarize splendidly (red and
green). In the rock, where the decomposition has not advanced
so far, there are still round, oval, and angular fragments, and,
finally, I found the cleavage-planes with the angle of olivine.

That olivine here also is the parent of serpentine is indu-
bitable ; but at the same time it is shown how the decomposi-
tion of the olivine took place. The olivine changed from
without into a gelatinous mass. This, as is well-known,
happens in areas ; and hence, as ehrysotile-th reads form at
the limits of the areas, the serpentine has afterwards the
appearance of chambers. The decomposition may thus be
followed piece by piece, and through all stages up to the struc-
ture of the Canadian specimens. The gelatinous mass no
longer polarizes ; but the newly formed serpentine mass pola-
rizes in the same fashion as all aggregated rocks ; a new
crystal-formation has commenced.

Thus in these two specimens the serpentine structure maybe
traced in accordance with the form that it took on in corre-
spondence with the action of the decomposing water, from the
imbedded and still perfectly preserved olivine crystal with
distinct cleavage-planes to the (formerly fluid) serpentine mass.
Conceive the olivine crystals gradually converted into a gela-
tinous matter. The latter must have deposited itself uniformly
in the calcareous mass, which was also still soft, and conse-
quently must have become round. Now the slightest vertical
pressure sufficed to give the gelatinous spheres a cylindrical or
lenticular form ; their section will always be a line, like that
of the Canadian Eozoon- rock. The intermediate passages
also occur. Further, everywhere on the serpentine, in places
at the points of contact with the limestone, there is the
u film ” or asbestos-layer, i . e. a crystallized layer with
needles.

In these specimens, therefore, we have the proof that the

278

M. Otto Hahn on Eozoon canadense.

chambers, the passages, and the “ film ” of the “ giant Fora-
minifer ” originated from olivine crystals ; therefore they are
pure mineral structures.

I have observed the same things even in the Canadian
rock ; only in it the olivines are not so fresh as in the former.
But as the serpentine mass occurs in exactly the same form
as there on the outer surface of the hand-specimen, the con-
clusion that both were originally in the same state, is per-
fec

certainly contain no Eozoon- structure. There is nothing in
favour of their owing their origin to a F oraminiferous test.

The question will now be raised, Do the canal-systems of
the Canadian rock also exist in the two hand-specimens?
No ; with the exception of one spot in a green mass which
does not polarize. It might, however, possibly be that the
mass of limestone was over- or underlying, and that the canal-
system occurred in the limestone. But this very spot also
exhibits the clear points (disseminated arragonite), with which,
according to my observations, the presence of the canal-system
is always associated, even in the Canadian rock. In all the
rest of the rock, in the thin sections, there is no arragonite
and no canal-system.

Let us now draw the direct conclusions : —

During the separation of the arragonite from the limestone,
water, or some other fluid containing lime, remained behind.
By existing pressure this penetrated into the soft limestone
mass in exactly the same way that every fluid penetrates into
another, denser one, in ramifications.

This may be regarded as hypothesis, although the expla-
nation is not far-fetched. It may be objected that this pro-
cess must also occur elsewhere.

But I have further been able to demonstrate these canal-
systems in the gneiss of Mont Blanc and the Schwarzwald —
nay, even in the syenite of the Plauenscher Grunde (Saxony)
and in the syenite of the Schwarzwald. I have observed
them in about thirty thin sections of these under crossed Nicols.
It is only thus that they make their appearance in the trans-
parent felspar and limestone, but then as beautifully as in the
Canadian specimens.

Thus from this side also, by the demonstration of a per-
fectly similar phenomenon in other rock, we obtain an expla-
nation of the canal-systems.

And thus the last character of the u giant Foraminifer ” is
got rid of — a character, however, which could not alone furnish
the proof of the organic nature of the -structures.

occur in serpentine rocks which

M. Otto Hahn on Eozoon canadcnse.

279

With this I might conclude my work. But as 1 do not
wish to fall short even in the smallest degree with respect to
the evidence in contradiction and its foundation, I pass on to

2. The Miner alogical Facts .

In the formation of the Canadian ifcsocui-serpen tines only
three minerals seem at the first glance to take part — dolomite,
serpentine, and limestone.

On closer investigation, however, other minerals occurred : —

No. II. has superiorly a chrysotile band^l millims. in breadth,
which is frequently repeated in the serpentine. Whenever I
ground the surface of the plate rather rough, a thread of silvery
lustre appeared eveiy where around the serpentine bands ; and
this was not merely asbestos-like, but actually asbestos, namely
chrysotile .

Besides chrysotile, arragonite occurs in disseminated clear
grains, and even in six-sided prisms.

The arragonite is surrounded by the same mass that forms
the canal-systems ; this is white by direct, brown by transmitted
light. When treated with acid, it dissolves at the same time
with the limestone . If the canal-systems were connected with
the chambers and, as Carpenter thinks, injected with serpen-
tine-mass from the latter, they would not dissolve at all in acid •
they must be serpentine and show the colour and polarization
of serpentine. Where there are serpentine grains, the same
white mass passes into the fissures surrounding the serpentine
grain. It is only in the alternating layers that the canal-
systems arc in the limestone ; and frequently their origin on the
disseminated arragonite grains may be distinctly detected.

Hence we get the following as to the formation of the
stone : —

The serpentine grains were originally olivine. During
their decomposition they swelled up, and in consequence burst
up the surrounding limestone, when the fluid white calcareous
mass entered into the fissure. But where the limestone mass
was still soft when the serpentine mass swelled up in it, either
the extending serpentine mass itself pressed the white calca-
reous fluid into the limestone, when the canal-systems were
formed, or a pressure was produced upon the whole mass, and
then the same effect occurred, only the immediate cause was
different.

It was undoubtedly cither a pressure from within, caused by
the decomposing olivine grains, or one from without upon the
whole mass, that produced the caual-systems. This is proved
even by their form. In the first place, they are quite irregular

280 M. Otto Halm on Eozoon canadense.

in their arrangement. Where they are arranged somewhat in a
spiral line, this is to be ascribed to the circumstance that the
calcareous layer itself, from which they originated, had already
a circular or spiral arrangement produced by pressure, as
is shown in specimen III. This, however, is accidental.
Usually they are irregular in arrangement, position, and form.
I have observed such a canal under a power of 750 diameters.
No trace of calcareous envelope, or of tubular form ; the picture
is rather that of a fissure ; the canal is quite irregular, thicker
or thinner, and in a zigzag direction.

In conclusion I have a remark to make with regard to the
limestone. This consists, like all primary limestones, of sepa-
rate individuals, distinctly separated from each other by their
lamination and a line, and in polarized light fully show them-
selves to be individuals by their different position. Many
individuals have the twin cleavage-gtlanes produced by pres-
sure. I have here to refer to the discovery of Prof, von
Reusch, who produced the cleavage-planes by concussion.
This phenomenon of itself indicates powerful pressure under-
gone by the mass after its solidification. Curiously enough
there are no canal-systems in the limestone individuals with
twin lamellae. Moreover a canal-system generally does not
extend beyond one limestone individual. This is easily ex-
plained. The fluid could penetrate only into a still soft indi-
vidual; it must therefore have found a limit at the next some-
what more hardened one. It must not be overlooked that the
canals, when they strike upon the serpentine mass or on
neighbouring individuals, become thicker, and terminate with
a kind of knob, the most certain evidence of a mass pushing
from behind and here coming to a stop.

The canal-systems occur only where the serpentine mass is
elongated, transparent, and yellowish ; therefore only where
the whole mass was visibly completely metamorphosed,
softened, in fact, into a pasty fluid, and pressed while still in
this state ; for only thus could the original olivine-forms be
converted into serpentine layers. Thus also are explained the
vertical lines in which the serpentine layers laterally strike
against a narrow limestone layer.

Thus, then, there does not remain much to be said about

3. The Zoological Facts.

If we glance back over the previous results we have, for
every part of the Eozoon (the chambers, the walls with
columns, the film, the intermediate mass with large passages,
as well as the canal-systems), not only an adequate geologico-
mineralogical explanation, but also the same phenomena in
rocks in which no one will speak of Ifoztfcui-structure, unless,

M. Otto Hahn on Eozoon canadense.

281

indeed, the canal-systems in gneiss must of themselves alone
be explained as of organic origin. I admit that I was for a
moment doubtful whether analogy for these structures in gneiss
might not be found in the sponges. I had, however, to re-
nounce this charming idea when I found that the canal-
systems consisted of quartz which traversed the felspar. Here
1 would recommend the further examination of this hitherto
unobserved phenomenon ; I believe that it throws a new light
upon the formation of gneiss.

It certainly does not conduce to exactness of inference if,
for the organic creature that is supposed to have been dis-
covered, we can find no complete analogue, and, for its separate
parts, again at least no exactly similar part in another creature.
Polytrema is regular. With the Acervulince , with which Max
Schultze arranges Eozoon , it has nothing in common except
irregularity — in such matters a resemblance of very doubtful
value. The Calcar nice have quite regularly arranged canal-
systems. The circumstance that our zoologists are accus-
tomed to preparations very different from rocks, and that they
have a preconceived notion that any symmetrical structure
cannot be inorganic, contributed not a little to the confusion.
I need only refer to the microscopic picture of the pitchstone
of Arran. But no rock is more deceptive in this respect than
serpentine. This greenish yellow transparent mass, with its
peculiar trembling lustre (caused by hyaline crystals) looks so
deceptively like sarcode, that it must not be taken amiss of a
zoologist if he is unable to tear himself free from the ideas
that press upon him at the first glance. If now, unfortunately,
the worm-like form is superadded, if the sarcode mass is
„ further clothed with an asbestos layer, and, lastly, we see
further u dentine-” and canal- or branch-systems, then it is
too much. Can it surprise us if another finds verrucose pro-
cesses? And yet nothing but illusion. Only a small amount
of quiet observation would at once have led back to the truth.
The observer must in fact have been puzzled at once by the
single fact that the canal-systems do not consist of serpentine
mass ; and this a glance into the microscope with polarized
light would immediately have shown. The canal-systems
always penetrate the chamber- walls of the Operculincv . Here
there is no trace of this, but rather a completely different filling
mass in the two. Nay a single olivine grain or calcareous
fragment in a chamber of Eozoon must fairly raise the question,
IIow can an olivine grain get into the chamber of a F ora-
minifer? On more careful observation, moreover, chambers
existing quite alone [i. e. grains) would have been found.
The chrysotile shell also is not regularly present ; where

Ann. May. N. Hist. Ser. 4. Vol. xvii. 11)

282 M. Otto Halm on Eozoon canadense.

present it cannot be mistaken by the geologist. But even as
to this shell the zoologists underwent a deceptio visits .

The serpentine mass is always round. If a chamber be cut
in any way except equatorially, the limestone mass of course
projects over the serpentine mass, and the one shines through
the other ; the inner angle of section now projects itself as a
line upon the surface of section ; and thus is produced the ap-
pearance of a shell, especially if asbestos needles are seated
upon the margin of the limestone, and partially project beyond,
it. We may easily convince oui selves of the illusion at
sinuations of the serpentine mass, as also in purely equatorial
sections.

Chrysotile layers are to be found in every serpentine. The
weathering of serpentine takes place in divisions ; and hence
the delusive walls.

How, it must further be asked, should a canal-system make
a dead stop before a crystalline individual? If the calcareous
shell were originally there, the canal-systems must have tra-
versed it in accordance with the law of organic structure. If
crystal-formation, or any other condition which destroyed the
canal-systems, afterwards occurred, this altered nothing in the
original arrangement of the canal-systems ; they could at the
utmost disappear here and there, and, indeed, in separate crys-
talline individuals, but must have been continued in the next
individual. But there is nothing of this hind . The separate
systems are rather completely limited in crystalline individuals,
from which it follows that the crystalline mass, nay, the lime-
stone, was in existence before the canal-system. These crys-
talline individuals are only commencements of crystal-forma-
tion. And finally we must ask why are there never canal-
systems in twin crystals? For the simple reason that these
had become hard, while the other parts were still soft.

As a last thing I will notice how improbable was the pre-
servation of the structures in the rock which bears in it such
distinct traces of having suffered violence.

I fancy from these statements of fact that the Eozoon , after
a brief but brilliant existence, is buried. It was indeed a
“ dawn animal.”

In conclusion, I offer my honoured teacher Prof, von
Quenstedt, of Tubingen, and Dr. von Hochstetter, of Vienna,
my best thanks for the liberality with which they have fur-
nished me with material for my investigation. Nor can I
omit to commend the admirable thin rock-sections of Mr. R.
Fnes, of Berlin.

My investigations were made with an excellent new
Hart nack’s instrument (VII. A), and with an English one by
Baker, of London.